The rule says that \(f(6) = f(5) + 11\) (we are using \(6 = n+1\) so \(n = 5\)). We don't know what \(f(5)\) is though. Well, we know that \(f(5) = f(4) + 9\text{.}\) So we need to compute \(f(4)\text{,}\) which will require knowing \(f(3)\text{,}\) which will require \(f(2)\text{,}\)… will it ever end?
in-context